Set the user-agent in the release name tool

Wikimedia requires an user-agent being set, so adding one to
the tool that fetches the robot page for release names.

Signed-off-by: Andrea Frittoli <andrea.frittoli@uk.ibm.com>

Author: afrittoli

tekton/release_names.go

@@ -72,6 +72,9 @@ func httpGet(url string) (*http.Response, error) {
 	if err != nil {
 		return nil, err
 	}
+
+	req.Header.Set("User-Agent", "golang-tekton-bot/0.1")
+
 	return http.DefaultClient.Do(req)
 }